A process for a sorting distribution sequence is understood to refer to the process of arranging items to be distributed in a sequence, which corresponds to the sequence of the distribution stops, e.g., based on house numbers/mail boxes. The distributor systematically approaches or accesses these distribution stops in his delivery region. A distribution stop in this case is not an absolute sorting goal, but a relative position in the distribution sequence.
This sorting when done manually is very involved. With the aid of a sorting machine, this sorting can be performed with considerably less time expenditure, wherein the sorting is based on a sorting plan. This sorting plan is a directory for coordinating addresses with defined delivery stops, meaning a list describing the sequence. In the machine, it is the relation between a machine readable address code and the sequence number. Since the number of delivery stops is higher than the number of sorting compartments in the sorting machines, the sorting distribution sequence for the items to be sorted takes place during several sorting passes. For this, the items are supplied once more to the sorting machine, respectively in the same sequence in which they were sorted during the previous pass.
The following example is selected as explanation:
Number of distribution stops NDPNS: 800
Number of items to be sorted NMPCS: 3000
Number of sorting compartments in the sorting machine NSTCK: 12
Number of sorting passes NPASS: 3
Maximum number of letters for each compartment NFILL: 260
With 10 sorting compartments, it is possible to sort for a maximum of 999 distribution stops during 3 sorting passes. This is done by sorting during the first pass according to the ones digit, during the second pass according to the tens digit and during the third pass according to the hundreds digit.
The characteristic marking of the respective distribution stop DPN can therefore be used for a direct coordination with the sorting compartments, meaning for DPN=356, the sorting during the first pass is to compartment 6, during the second pass to compartment 5 and during the third pass to compartment 3.
Since the sorting machine comprises 12 sorting compartments, but only 10 compartments are needed for sorting during each pass, a situation where the compartment are full can be handled by assigning items to so-called overflow compartments. As soon as a sorting compartment is full, additional items for this compartment are redirected into an overflow compartment. When emptying the machines, a suitable operating guide ensures that the items from the original compartment and those from the associated overflow compartment are combined. If the number of sorting compartments that are filled exceeds the number of available overflow compartments, the sorting pass must be stopped, so that the operator can create space for additional items by emptying the respective compartment.
With this state of the art sorting process, sorting compartments can overflow or can be filled with only a very small number of items. Overflow compartments are made available because of the overflow possibility. However, this reserving of overflow compartments means a reduction in the sorting capacity of the sorting machine with respect to the possible distribution stops.
A successive optimizing of the sorting plan can reduce the number of necessary overflow compartments, but cannot replace these because the composition and the scope of the items remain unknown. When emptying the sorting machine and combining the content of the sorting compartments and overflow compartments, operating errors can occur, which may change the sequence in some cases to such a degree that the sorting must be repeated.
On the other hand, the use of overflow compartments does not ensure that other situations with full compartments cannot occur.
U.S. Pat. No. 5,363,971 discloses a process for avoiding compartment overflows, wherein the zip codes are read and assigned the distribution stops. Following this a microprocessor modifies the assignment of the zip codes to the distribution stops in order to optimize the distribution of the items in the compartments. This is done by not using all possible distribution stops, but providing reserve stops. A special coordination of the zip codes with the distribution stops makes it possible to distribute the items in an optimum manner, so as to minimize the probability of compartment overflows. Following that, the remaining number of items only are sorted into the original combination of compartments, which results in an undesirable, uneven filling of the compartments.
Low filling levels of the sorting compartments result in time losses because the time expenditure for emptying a compartment with low filling level does not differ or only insignificantly from that for emptying a full compartment.
It is the object of the invention to create a process for sorting distribution sequences in an item sorting machine, which process prevents the occurrence of full compartments while, at the same time, distributing the items as uniformly as possible into the compartments, so as to avoid additional overflow compartments and which makes it possible to use only enough sorting compartments as are needed for the actual number of items and the item composition in order to ensure an optimum filling of the compartments.
The above object given by is achieved according to the invention and a process for sorting distribution sequences in an item sorting machine, for which each item is arranged in a distribution sequence in accordance with its read and identified address code, wherein the sorting occurs during several passes in dependence on the number and size of the existing sorting compartments, as well as the number of the distribution stops describing the distribution sequence, and wherein: that following knowledge of the complete address coding for all items and to avoid full-compartment situations, using iterative search steps in a simulation of the sorting process prior to the sorting process that is carried out in the item sorting machine with up to n modified distribution stops, wherein n represents the total number of distribution stops that can be processed by the item sorting machine, which are formed during the passes as compartment combinations from the combinations of the characteristic numbers of all available sorting compartments, the items of each original distribution stop are distributed to modified distribution stops or compartment combinations while retaining the predetermined distribution sequence in such a way that the sorting compartments can accommodate the items arriving for distribution without exceeding the filling level, so that following the simulation, the sorting can occur in the item sorting machine. The assumption here is that the sorting capacity of the sorting machine as a rule is higher than the necessary capacity based on the item composition, thereby resulting in sorting compartments or sorting goals remaining unused.
As a result of the process according to the invention, these unused sorting goals/distribution stops are incorporated into the sorting process, starting with the fact that the sorting goals/distribution stops characterize only the relative position in the sorting sequence. For this, the original distribution stops are changed to modified distribution stops, meaning the same specified sequence for two different number systems. The process results in an automatic adaptation to the actual conditions of a sorting pass with respect to the number of items and the item composition with optimum use of the machine capacity.
The following advantages result:
Reduction in the operating time for the machine by preventing machine stops, caused by situations where the compartments are full;
Reduction in the number of operating errors, which can occur when emptying the sorting machine when combining the contents of sorting compartments and overflow compartments.
The advantageous embodiment according to patent claim 2 demonstrates that if the compartments are filled insufficiently, the number of compartments used are reduced until the predetermined optimum degree of filling is reached. This reduces the expenditure for emptying the machine since the actually needed number of compartments only are used.